Choose from our line of modulators and driver electronics
Conoptics manufactures an extensive line of low voltage electro-optic light modulators, driver electronics, and associated components to satisfy your diverse requirements.
Your application will dictate which versions of modulator and driver electronics you need and what auxiliary components you should use. Most often, the first application requirements considered in the choice of modulation system components are the information bandwidth and waveform requirement. Standard Conoptics products include eight general purpose drivers. Just view that information on the specifications tab to learn the characteristics of standard products and their operating parameters.
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Specifications
Drive Electronics
In general, the first application requirements considered in the choice of modulation system components are the information bandwidth and waveform requirement. The driver output voltage achievable is a function of amplifier bandwidth and, while this system parameter is not isolated from others, such as aperture diameter, operating wavelength, etc., it is normally the limiting parameter of the system.
Optical Modulators
All modulators listed in this data sheet are of the transverse field type, that is, the electric field produced by the applied signal voltage is perpendicular to the optical propagation direction. The voltage swing required by a given modulator at a given operating wavelength to transit between the full off state to the full on state is called the Half Wave Voltage (V½). The transverse field structure allows reduction of V½ by manipulation of the crystal length to aperture ratio to a level achievable by available driver electronics. V½ is roughly proportional to wavelength and long wavelength devices usually require higher length to aperture ratios to accommodate existing driver output levels. Conoptics offers modulators constructed with three different crystal species: Ammonium Dihydrogen Phosphate (ADP), Potassium Dideuterium Phosphate (KD*P), and Lithium Tantalate (LTA). Models 370, 380, and 390 utilize ADP as the active element. The unique feature of these models is the virtual non-existence of piezoelectric resonances. Models belonging to the 360 series utilize LTA. LTA has the lowest intrinsic V½ and the longest wavelength IR cutoff. Furthermore, it has a combination of high refractive index and relatively low dielectric constant which allows modulators to be designed which make full use of the intrinsic driver frequency response. Models in the 360 series exhibit piezoelectric resonances but they are discrete and very narrow. KD*P is used in Model 350 series modulators. In terms of optical transmission bandwidth and driver frequency response utilization, this series falls in between ADP and LTA versions. Table 1 below provides the specifications our ADP (240-to-800nm), KD*P (240-to-1100nm) and LTA (700-2000nm) series modulator product line.
Modulator Modifications
Any of the modulators listed here can be used as a phase modulator by simply rotating the input polarization direction by 45°. This procedure makes one of the modulator half segments essentially inactive and doubles V½ (now the voltage required for a 180° phase shift). A factory modification can be made during construction which restores V½ to its original value. This modification precludes use of the device as an intensity modulator, however, and is irreversible.
Amplifier Specifications
Table 2 listed below provides the basic specifications of our line of amplifiers and the interface configuration to the modulators. All of our amplifiers include a DC Bias Supply with greater than +/- 250 volts for setting the modulators operating point. The lump capacitance amplifiers have (2) BNC cables driving the modulator push-pull. The 50 ohms S.E. configuration has (2) SMA connectors for driving a 50 ohm single ended modulator and a third connector (BNC) for DC Bias. The 100 ohm and 50 ohm balanced line configuration has (2) twinax connectors for driving a balanced line modulator and a third miniature twinax connector for the DC Bias.
Modulation Systems
The modulators and drivers listed in this data sheet can be used in various combinations to form high performance, cost effective modulation systems. Table 3 shows the key performance characteristics of various combinations of standard driver electronics and modulators. The high frequency -3dB points may be limited either by the driver or the modulator. Rise and fall times are normally calculated as 0.35 divided by the -3dB bandwidth but, due to the compression caused by the sine squared transfer characteristic over its full on to off range, the optical rise and fall times of these systems is approximately 20% less.
PHASE MODULATORS
The standard modulators 350, 360, 370, 380 and 390 series are built as intensity modulators with a polarizer aligned to the crystal axis. The same modulators can also be configured for use as polarization rotators, voltage variable wave plates or phase modulators. However, when used as phase modulator only half the cell is active, so the half wave voltage is twice as high as compared to the standard use.All of our modulators can be constructed with all the crystals inline such that the full cell is active as a phase modulator, but in this configuration it cannot be used as an intensity modulator, polarization rotator or variable wave plate. Once the modulator is built as a phase modulator it cannot be re-configured as an intensity modulator.
